Frequency responsive relay



Dec. 20, 1955 p, BEER 2,728,003

FREQUENCY RESPONSIVE RELAY Filed Feb; 13, 1953 INVENTOR ATTORNEY5 UnitedStates Patent FREQUENCY RESPONSIVE RELAY Palle Finn Beer, Lidingo,Sweden, assignor to Svenslra I Alttiebolaget Gasaccumulator, Lidingo,Sweden, a con poration of Sweden Application February 13, 1953, SerialNo. 336,841 Claims priority, application Sweden February 27, 1952 7Claims. v(Cl. 310-413) The present invention refers to afrequency-responsive electrodynamic relay, more particularly, a relay ofthe type comprising a loop conductor movable in a permanent magneticfield. In this type of relays, the leads for the current supplied to orderived from the relay often present difficulties in that frictionforces and directing forces of an unpredictable nature are encountered.

It is anobject of the invention to provide a relay that is free from thedisadvantages referred to, and, also, to provide in a relay of the typereferred to good selectivity even at very low frequencies, means beingprovided for' adjusting the selectivity.

The frequency-responsive electrodynamic relay accord ing to theinvention comprises means for creating a mag-.

netic field, and a first loop conductor movable in said field, the relaybeing characterized in that said loop conductor comprises two portions,one portion forming the secondary of a transformer adapted whenenergized to induce a current in the loop, the other portion beingpositioned in'said, magnetic field, thereby to impart motion to saidloop in response to current induced therein.

The movement performed by the loop under the influence of an appliedvoltage may be utilized in various ways. It is thus possible, accordingto an embodiment of the invention, to let the movable loop controldirectly a contact for making or breaking a circuit so as to pro vide avibrator or rectifier arrangement. According to another embodiment, thefirst loop is made to. drive mechanically a second loop, whichoscillates in a second permanent magnetic field. The second loop formsthe primary of a transformer, the output voltage of which has anamplitude which is determined by the frequency of the applied voltageand by the resonant frequency of the relay.

The invention will be described below as illustrated in the drawing inthe form of an embodiment whose principle of operation is substantiallyof the lastmentioned type. Fig. 1 shows an elevation of the relay2,728,003 Patented Dec. 20, 1955 portions joined by a narrow thereforehas two wider slot.

The relay is provided with means for producing a controllable directingforce for holding the disc in its neutral position when it is notcarrying current. The arrangement is such as to make the directing forcefree from friction effects and to make it possible to adjust the samecontinuously from zero to its maximum value. A strip 17 of iron isattached to the aluminium disc 5 and is influenced magnetically by thefield of a permanfllt magnet havingpole shoes 18 and 19. The magnet 20has the shape of a flat circular disc and is magnetized so as to havepoles at diametrically opposed points in the manner indicated in Fig. l.The magnet 20 is rotatable and it is apparent that, in the positionindicated in the drawing, a strong magnetic field is formed in partialsection and Fig. 2 a top plan view of the same. Fig. 3 illustrates adetail of the relay.

The relay comprises a frame of nonmagnetic material having a bottompiece 1 and two wall pieces 2 and 3, onto which is screwed a lid 4. Thetwo conductor loops are formed by two portions 5 and 6 of an aluminium 1disc or plate, which is supported by a shaft 8 journalled' in a pair ofscrews 7 in the lid and the bottom, respec tively. The disc portion 5has therein an aperture 9, through which extends a transformer core 11and a permanent magnet 13. Similarly, the disc portion 6 has an aperture10 for a transformer core 12 and a permanent magnet 14. The portions 5and 6 are electrically insulated from each other so that a currentinduced in one portion does not reach the other. The cores 11 and 12 areprovided with windings l5 and 16, respectively, which are connected toexternal circuits for the relay.

The apertures 9 and 10 are shaped so as to let each of the correspondingloops enclose as completely as possible its transformer core and magnet.Each aperture between the pole shoes 18 and 19, and that this field isgradually diminished down to zero value as the magnet is turned to aposition at right angles to the initial one.

Each of the pole shoes 18 and 19 may be provided with an extension 23 or24, respectively, in accordance with Fig. 3, in order to concentrate thedirecting force to the longitudinal plane of symmetry of the relay. Thepole shoes are held in position by an intermediate nonmagnetic member,which serves also the purpose of accommodating the uppermost journallingscrew 7. Besides providing a fixed zero position for the disc 5 thedirecting force is also adapted to determine the resonant fre quency ofthe oscillating system. Thus, the frequency is highest when the magnetis in such a position that the directing force has its greatest valueand decreases with a decrease in the directing force.

The magnet 13, which produces the magnetic field for driving the loop 5,is supported by the wall member 2 and is so positioned as to make theloop 5 oscillate always on the same side of the neutral plane of themagnet. This makes the relay unsensitive to the second harmonic of theresonant frequency to which it is tuned. A displacement of the magnet 13alters the character of the magnetic field in which the loop 5 isoscillating. This alters the damping of the oscillatory circuit of whichthe loop 5 forms a part and so also the Q of this circuit. It is thuspossible in a simple manner to alter the shape of the resonance curveand thereby the selectivity of the relay.

It is apparent that the magnetic field deriving from a current throughthe loop 5 will interact with a radially directed magnetic field fromthe magnet 13. In the event that it is of importance that the circuit Qshould be independent of the oscillatory amplitude of the loop 5 careshould be taken that the loop 5 is always oscillating in a homogeneousfield. Such a field may be obtained, for example, by providing for themagnet 13 an elongated pole shoe and positioning the magnet so that theloop is always Within the area corresponding to the pole shoe.

The loop 6 is driven by the loop 5 and moves in the field from themagnet 14, which is inserted in an aperture in the wall members 2 and 3and is so positioned that the neutral position of the loop 5 is in theneutral plane of the magnet. This causes the damping to be small forsmall amplitudes of the oscillation, so that the oscillatory system iseasily started. Furthermore, the current induced in the loop has doublethe frequency of the oscillation. This is particularly advantageous whenthe relay is tuned to a very low frequency of only a few cycles persecond and the output voltage of the relay is applied to an amplifier inthat the circuit elements of the amplifier can then be of more suitableproportions. Also, no voltage is induced at small amplitudes, althoughthe voltage increases sharply with increased amplitudes.

The voltage to be analyzed is applied to the transformer winding 15 viathe connecting terminals 25. The alter- 6. The oscillations performed bythe loop'zf at the resonantfrequency of the relay make the loop 6oscillate in afcor responding manner in the field of the magnet 14. Thisgives rise to a voltage which is transformed into a higher voltage inthe right hand transformer, and which can then be derived from thewinding 16 through the connecting:

terminals 26.

As will be apparent from the above description, the disc. forms twoloops of two electrodynamic systems-one of.

the loops functioning as the secondary of an input trans 20 former andthe other loop functioning as the primaryof'. an output transformer.Furthermore, the loops'a-reudrectly joined to each other in such a waythat the sec ondary of the one transformer drives mechanicall-yi-theprimary of the other.

The frequency-responsive relay according to the invention has severaladvantages. It is tunable to and is. char-t acterized by a markedsensitivity and selectivity atiwery, low frequencies. The frequencycharacteristic of titer-re lay and the resonant frequency thereof arevcontinuously 1 adjustable independently of each other. -The,.,1nagnetic,directing force gives a resonant frequency which -is1i;ndc-'. pendent ofthe oscillatory amplitude. The .relay is'me-J chanically balanced, whichmakes it insensitiverto external: mechanical influences of a kind thatisapt to arise idem-,1. nection with use in vehicles of variouskindsFinallygthe s relay doubles the applied frequency, which facilitates:the proportioning of succeeding amplifying stages, particularly-- atlow frequencies. 2-1.-

What I claim is: #140 l. A frequency responsive relay havingafirstportion' anda second portion, said first portion comprising, -.awri mary winding, a first movable loop conductor and a first permanentmagnet, said primary winding having a mag netic core, said first loopconductor encircling both atpor tion of said magnetic core and aportionof said first-.pe'r---. manent magnet; said first permanentmagnet, and saidwinding when energized by a varying current, each.beingfadapted to create a magnetic field in said loop, the fieldin said loopcreated by said permanent magnet interacting 5 with the magnetic fieldcreated by said winding to cause said loop to oscillate in resonancewith said energizing,

ing,. a second movable loop conductor, and a secondpermanent magnet,said second winding having a magnetic core, said second loop conductorencircling both a portion of the magnetic core of said second windingand a portion of said second permanent magnet, said second movable loopconductor being'electrically insulated from but rigidly joined with saidfirst loop, to be actuated there by; said second loop having arelationship of being the primary of an output transformer, whereby anoutput current is generated in said second winding due to theoscillation of said movable loop conductors.

2. The relay as defined in claim -1 .wherein said first permanent magnetis adjustable With respect to said first movable loop conductor, wherebyit is possible to alter the shape of the resonance curve of the relay,and thereby alter the selectivity of the relay.

3. The relay as defined in claim 1 wherein means are able loopconductors will oscillate,

-4. The relay as defined in claim l-wherein said mow.

able loops when connected together, take the forrnof-an elongated plate,said plate being rotatably mounted upon.

a shaft, so as to be able to oscillate thereabout.

5. The relay as defined in claim 4 wherein said plate;

has magnetized portions atdiametrically opposed locations with respectto said shaft; a'movable pole magnet generally aligned with said shaftand capable of being ad justedwith respect to said magnetized portions,wherebyv the resonant frequency of the oscillating system can be set. It

6. A frequency responsive relay comprising, first, and second movableloop conductors, said loops being electrically insulated from each otherbut rigidly joined so as to be able to oscillate together; a permanentmagnet and a winding having a magnetic core, associated with each. loop,and encircled thereby, sothat upon a varying current;-

being impressed uponthe winding associated withsaid first loop, theloops may be caused to oscillate, and a cur rent to be thereby generatedin the winding associated;

with said second loop.

7. The relay as defined in claim 6 wherein means are; provided forselecting the frequency at which the loops,

will oscillate.

' References Cited in the fileof this patent UNITED STATES PATENTSPrince Dec.- 26,1933"

